Dosing systems exist which are configured for repeatable, metered dispensing of fluids, such as medicines. The dosing systems generally include a pump system that drives a predetermined volume of fluid through tubing to a needle or nozzle assembly, which delivers the fluid into a container.
Various types of pumps can be used in such dosing systems. One such pump is a positive displacement pump. Positive displacement pumps generally incorporate a piston driven pump unit that includes a piston, a fluid chamber, and a body. The pump unit is used, in combination with timed valves, to encourage fluid travel through the pump chamber and the tubing. As compared to other pump systems, such as peristaltic pump systems, these positive displacement pump systems provide high speed, repeatable volume fluid delivery. Examples of positive displacement pumps are shown in U.S. Pat. No. 3,880,053, assigned to TL Systems Corporation, and U.S. Pat. No. 5,540,568, assigned to National Instrument Co., Inc. U.S. Pat. No. 5,540,568 describes a filling system including a rolling diaphragm incorporated into a disposable pump head module. In that system, the pump head is releasably sealable to a pump body, and includes a rolling diaphragm when disconnected from the pump body.
Certain positive displacement pump assemblies, including those mentioned above, incorporate a rolling diaphragm to separate the piston drive unit from the fluid chamber. The rolling diaphragm provides a number of advantages when used in a positive displacement pump. The rolling diaphragm provides a leakproof seal for the fluid within the pump. It also ensures gentle handling of the fluid to be delivered by minimizing the shearing of molecules within the liquid that may otherwise occur using a piston drive unit to drive the liquid. The rolling diaphragm also prevents the frictional wear of the piston drive unit from causing contamination of the fluid.
The existing positive displacement pumps and systems incorporating these pumps have a number of disadvantages when used in sterile operations. The manual disassembly, cleaning and re-assembly of these pumps and systems as well as additional clean-in-place and sterilize-in-place operations subtract time from operation of the dosing system and add significant cost to operate these types of systems. These process critical, yet required operations for sterile use of these existing positive displacement pumps and systems, offer opportunity and risk of accidental and unknown contamination thus compromising any product filled with said or suspect pump systems. Additionally, wear of the piston unit against the inner diameter of the body unit in existing positive displacement pumps (i.e. with out the use of a rolling diaphragm) can cause contamination of the sterile fluid during aforementioned sterile and clean product filling operations.
For these and other reasons, improvements are desirable.